Client does not connect to host on older iMac

Nextcloud version: Version 2.6.3legacy (build 20200217)
Operating system and version: macOS 10.10.5 (Yosemite)

The issue I’m facing:

The Client does not connect to the Host since january 6th 2021
From other devices (e.g. Linux-laptop) the same host connects and syncs just fine.

I know I run an older build of the NC client, though this is the newest one that ran on my OS when installed, and I cannot update the OS on the iMac to any newer than that (not possible due to Apple not allowing updates any longer).

I tried to download a slightly newer legacy build (2.6.5legacy) from the nextclod homepage ( but it will not download completely (no matter to what device I download: Download stops just at 98% or so … ), so that is also a dead end.

What else could I do to get the NC client on my good ole 2009 iMac back to work?

Thanks for any light you can shed,

Is this the first time you’ve seen this error?: N

Steps to replicate it:

  1. Just start it
  2. See it does not sync
  3. Look at settings page: Message says: "No connection with "